UV spectrophotometric study of the kinetics and mechanism of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates and NH-acid

Abstract

To determine the kinetic parameters of the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of an NH-acid, such as 2,3-di-hydroxybenzaldehyde, the reactions were monitored by UV spectrophotometry. The second order fits were automatically drawn and the values of the second order rate constants (k 2 ) were calculated using standard equations as part of the program. The dependence of the second order rate constant (lnk 2 ) on the reciprocal temperature was in agreement with the Arrhenius equation, in the temperature range studied, providing the relevant plots to calculate the activation energy of all reactions. Furthermore, we evaluated the effects of solvent, structure of different alkyl groups within the dialkyl acetylenedicarboxylates, and their concentration on the rates of reactions. The proposed mechanism was confirmed by experimental results and steady-state approximation. The first step (k 2 ) of the reaction was recognized as the rate determining step on the basis of experimental data.

A Mechanistic Investigation of Stable Phosphonate Ester Derived from 3, 4 dichloro Aniline: A Kinetics Study and Theoretical Calculations

“…In fact, in recent works triphenyl phosphite has been used instead of triphenylphosphine in the previous work. [33][34][35][36][37][38][39][40][41] In addition, the product is phosphonate esters 4 not phosphorus ylides. Synthesis of compounds 4, shown in Figure 1, has been reported earlier.…”

Preparation of Stabilized Phosphorus Ylides via Multicomponent Reactions and Their Synthetic Applications

“…A plausible mechanism for the formation of ylides in this reaction is shown in Scheme 1. The reaction starts from addition of TPP (1) to electrondeficient acetylenic ester (2) to form the zwitterionic intermediate (3) [39][40][41][42], which is subsequently protonated by the acid (4) to give vinyltriphenylphosphonium cation (5). Then, addition of the conjugate base of the acid (4) to (5) produces ylide (6) (Scheme 1).…”

“…Compounds (44) apparently result from the initial addition of the phosphine to the acetylenic ester and the concomitant protonation of the 1:1 adduct, followed by attack the enolate anion to form the intermediate (41), which is then converted to the butyrolactone (44) presumably by elimination of HCl and ring closure (Scheme 13) [66]. Ethyl oxo-(2-oxo-cycloalkyl)-ethanoates (45) undergoes a smooth reaction with TPP (1) and DAAD (2) via intramolecular Wittig reaction to produce spiro-cyclobutene derivatives (47).…”

Kinetic and Mechanistic Investigation of Pyrano[2,3-d]pyrimidine Formation in the Presence of Catalyst under Novel One-Pot Three-Component Reaction

“…Kinetics and mechanism of numerous reactions have been previously studied using the UV-vis technique [24][25][26][27][28]. In recent years, we have endeavored to expand the synthesis of phosphorous ylides along with developing experimental and theoretical studies on the kinetics and mechanisms of these reactions [29][30][31][32][33][34][35][36]. In these studies, reactions occurred by at least three steps.…”

“…Moreover, the overall reaction order followed second-order kinetics. The rate of all reactions was increased in solvents with upper dielectric constant value that could be related to the differences in stabilization of the reactants and the zwitterionic intermediate by the solvents [29][30][31][32][33][34][35][36]. In present work, we describe kinetic results together with detailed mechanistic studies for the one-pot, three-component condensation reactions consisting of 4-nitrobenzaldehyde 2, malononitrile 3, and thiobarbituric acid 1 in the presence of sodium acetate as a catalystin methanol and environmental friendless solvents (mixture of ethanol and H 2 O 50/50) based on a global kinetic analysis methodology using the UV-vis spectrophotometry apparatus.…”